Originally Posted by
ninefinger
If you are buying a new machine then work hard on the distributor to have it supplied with the spindle of your choice, i.e an ISO30 / BT30 spindle should be readily available for these machines (better for europe I believe) or R8 (more USA), but not MT4 which will be a real pain for tool changes.
A general note about what I've written below - I believe in a "balanced" design, not overkill on one thing and limited on another. No point doing that as the added capability is often never used and can often be detrimental overall.
For ball screws, there will be no difference between the 16mm and 20mm on X and Y except to make it harder (a lot harder) to fit the X if you go bigger. Y is relatively short so has perhaps a very small benefit for the 20mm if you run it unsupported at one end (might be less prone to whip at very high speeds) but I don't notice on mine any problems (unsupported 16mm on Y).
The bigger you go the more money you will spend...on end support bearings too.
As for steppers vrs AC servos vrs ? Looks like the Leadshine offering might get my vote now based on my past experience. Steppers (ie higher torque at low speeds, less torque at high speeds) can direct drive a ballscrew, versus belt and pulley for servos (which I did). At the end of the day both will do the job equally well, but the steppers in this case will likely be an easier fit, and maybe a touch less costly due to not needing 6 pulleys and 3 belts.
Also, the Leadshine is nice to be able to get AC powered drives (no extra power supply required - but only in the big sizes). Simplifies wiring.
As for sizing - well, its your money but overkill means overpaying. 200 inches per minute sounds cool, until you try it on the Y axis from home position. In less than 2 seconds you're at the end of the travel - better have reliable limit switches! And limit switches won't protect you from crashes into your vice, workpiece, etc. More power = more broken!
To be realistic, you don't need alot of power on X and Y. I have DC servos rated at 50 oz-in with 4:1 reduction (ie 200 oz-in at the ballscrew) and can accelerate very quickly and go too fast for my liking (120 inches per minute) Because steppers have a different torque curve you need a higher torque rating to not have the torque drop off too much at speed, but a 600 oz-in is plenty for x and y.
Thats enough for now.
Mike
ZX7045 new build
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